Steam reforming, sometimes referred to as steam methane reforming, typically uses an external source of hot gas to heat a plurality of reformer tubes in which a catalytic reaction takes place that converts steam and lighter hydrocarbons such as natural gas (methane) or refinery feedstock into hydrogen and carbon monoxide (syngas). Syngas reacts further to give more hydrogen and carbon dioxide in the reactor. The carbon oxides are typically removed before use by means of pressure swing adsorption with molecular sieves for the final purification. The pressure swing adsorption works by adsorbing substantially all impurities from the syngas stream to leave a relatively pure hydrogen gas.
Steam methane reformers are widely used in industry to make hydrogen. Examples of steam methane gas reformers are disclosed in U.S. Pat. No. 6,759,016 to Sederquist, U.S. Pat. No. 7,037,485 to Drnevich et al., and U.S. Pat. No. 7,919,057 to Genkin et al., which are each incorporated by reference herein in their entirety.
For example, as shown and described in U.S. Pat. No. 6,759,016 to Sederquist, a catalytic hydrocarbon fuel steam reformer converts a fuel stream, comprising, for example, desulfurized natural gas, light distillates, methanol, propane, naphtha, kerosene, and/or combinations thereof, and water vapor into a hydrogen-rich reformate stream. It includes a reformer vessel having a shell and a header. The interior walls (including the top and bottom) of the vessel have an insulating layer. Disposed within the vessel are a vaporizer, the shell containing a reforming section, and a burner. In operation, a pressurized mixture comprising fuel and water is fed from the vaporizer inlet and is injected into the vaporizer. The fuel/water mixture flows within the vaporizer and is heated by heat exchange with the burner exhaust stream exiting the reforming section to produce a process stream comprising vaporized fuel and steam. The reactant stream exiting the vaporizer is supplied via a vaporizer outlet to the reforming section. The reactant stream exiting the vaporizer outlet is supplied to a reactant plenum, where it is distributed via feed tubes to reformer tubes. Reformer tubes are disposed within burner tubes that are fixed to a burner tube plate.
Despite previously proposed reformer systems, there remains a need for an improved reformer tube assembly for steam reformers.